So i just brewed this up and was entering the recipe into beersmith and noticed the ibu on the included instructions way off from beersmith. The instructions show ibu around 20-23 which is in line with a traditional bock but beersmith came up around 9.

Recipe:
Steeping grains
8oz caramel 120l
4oz chocolate
4oz carapils

Fermentables
6.6 lb munich lme
2lb golden light dme
8;z maltodextrin

Hops
.75oz cluster bittering
.25 mt. Hood aroma

1 pkg brewferm lager yeast

I replaced the yeast with white labs german bock and added yeast nutrient and irish moss

Am i crazy or is the hops bill way too light?
If i did a full boil the hops would bitter at just about 20ibu but since extract brews are 2.5gal boils the recipe sheet usually is adjusted to reflect lower utilization.

I get that the boil size is throwing it off but i've never had problems before... ot sure why this one is throwing it off

It's a funny thing in Beersmith. It takes boil gravity into account (which is incorrect) and for lower IBU beers it always does it that way. Just fix the boil volume to the wrong amount (I know, sounds weird), and it'll be fine with the cluster you have.

__________________Broken Leg BreweryGiving beer a leg to stand on since 2006

It's a funny thing in Beersmith. It takes boil gravity into account (which is incorrect) and for lower IBU beers it always does it that way. Just fix the boil volume to the wrong amount (I know, sounds weird), and it'll be fine with the cluster you have.

So the final result should be balanced to the style regardless of what beersmith or android brewer app says and the mfg ibu is correct?

So the final result should be balanced to the style regardless of what beersmith or android brewer app says and the mfg ibu is correct?

It used to be believed that IBUs were impacted by wort gravity, and it's since been disproven. If you boil a given amount of hops in a given amount of solution, the IBUs will not change based on the gravity of the wort. The calculators haven't taken this into consideration- and I"m not sure they ever will as I don't think it's an easy fix in the software.

The only thing I know of that does impact hops utilization in a partial boil is the fact that the beer is "topped off". That's not an issue for a beer like yours, but in a huge IPA where you want to have a ton of IBUs- say, 80, it may be an issue since there is a maximum of hops oils that can be isomerized in liquid. That is generally thought to be around 100 IBUs. So, taking a 100 IBU wort and adding a 0 IBU water addition would mean a reduction in the IBUs. If you had 100 IBUs in 2.5 gallons, and then topped off with 2.5 gallons of water (0 IBUs) then the IBUs would be 50 at most.

That has nothing to do with wort gravity, though- that's just the nature of hops oils and isomerization.

In most beers, this isn't at all a concern and it's the software that is giving you such a low IBU guestimate.

__________________Broken Leg BreweryGiving beer a leg to stand on since 2006

It used to be believed that IBUs were impacted by wort gravity, and it's since been disproven. If you boil a given amount of hops in a given amount of solution, the IBUs will not change based on the gravity of the wort. The calculators haven't taken this into consideration- and I"m not sure they ever will as I don't think it's an easy fix in the software.

The only thing I know of that does impact hops utilization in a partial boil is the fact that the beer is "topped off". That's not an issue for a beer like yours, but in a huge IPA where you want to have a ton of IBUs- say, 80, it may be an issue since there is a maximum of hops oils that can be isomerized in liquid. That is generally thought to be around 100 IBUs. So, taking a 100 IBU wort and adding a 0 IBU water addition would mean a reduction in the IBUs. If you had 100 IBUs in 2.5 gallons, and then topped off with 2.5 gallons of water (0 IBUs) then the IBUs would be 50 at most.

That has nothing to do with wort gravity, though- that's just the nature of hops oils and isomerization.

In most beers, this isn't at all a concern and it's the software that is giving you such a low IBU guestimate.